Method for measuring location of radio frequency identification reader by using beacon

ABSTRACT

The present invention relates to a method for measuring a location of a radio frequency identification (RFID) reader by using beacons, and an RFID system for measuring a location of a moving RFID reader in an RFID system comprising: a plurality of beacon devices for emitting beacons; an RFID tag for transmitting pre-stored information by using radio frequency identification; and an RFID reader for calculating a current location using a plurality of at least three beacons wherein the RFID reader receives the plurality of beacons from the plurality of beacon devices while moving, and receiving the information from the RFID tag by using the radio frequency identification. According to the present invention, it is possible to increase the accuracy of the location measurement of a moving RFID reader in an RFID system because the location of the RFID reader is measured in consideration of propagation environments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a broadening reissue of U.S. Pat. No. 8,629,773,issued on Jan. 14, 2014, which is a continuation of International PatentApplication No. PCT/KR2008/002906, filed May 23, 2008, which is basedupon and claims the benefit of priority to Korean Patent Application No.10-2007-0050316, filed on May 23, 2007.

TECHNICAL FIELD

The present invention relates to a method for measuring a location of aradio frequency identification (RFID) reader by using beacons, and anRFID system for the method. More particularly, the present inventionrefers to a location measurement method for easily and accuratelymeasuring a location of a moving radio frequency identification (RFID)reader in an RFID system, and the same RFID system, in such a mannerthat the RFID system includes a plurality of beacon devices, which arefixed at predetermined locations and emit beacons including referencelocation information about their own locations and,signal-intensity-to-distance information, and that the RFID readerreceives beacons from at least three beacon devices, identifies relativedistances from the respective beacon devices by usingsignal-intensity-to-distance information included in the beacons, andcalculates its own location through a triangulation method.

BACKGROUND ART

Location-based technology is a technology of acquiring information aboutthe physical, geographical, and logical locations of an object (a personor thing) placed at a specific location, and appropriately reactingaccording to the acquired information. The conventional positioningmethods include a triangulation method of determining a location bymeasuring a difference of distances between objects, an angle betweenthem, or an azimuth angle between them, a scene analysis method using ascene viewed from a specific vantage point, and a proximity method offinding an object by approaching a specific location.

Recently, with the development of wireless communication technologies, aradio frequency identification (RFID) system has been highlighted as newwireless network technology, and has been widely used. It has beenrequired to develop a technology of measuring a location indoors oroutdoors by using the RFID system, and such a technology can be utilizedfor various purposes, such as collecting data by means of RFID in aninaccessible area, transmitting the collected data to users, etc.

Meanwhile, conventionally, there are various location measurementtechnologies, including a location measurement technology using a globalpositioning system (GPS), a location measurement technology using areceived signal strength indication (RSSI) of a radio frequency signal,a location measurement technology using local-area wirelesscommunication, etc.

The location measurement technology using a GPS is a technology ofmeasuring a distance to a GPS satellite, which orbits the earth, bymeasuring the phase of a carrier signal sent from the GPG satellite(i.e. by absolute positioning) or by tracking the code of the carriersignal (i.e. by relative positioning). Since the location measurementtechnology using a GPS has wide signal coverage, and can stably provideservice through a fixed satellite, it is currently the most widely used.However, the location measurement technology using a GPS hasdisadvantages in that precision is low, and that service is unavailablein shadow areas or indoors where GPS satellite signals cannot bereceived.

The location measurement technology using mobile communication is atechnology of obtaining information about the geographical location of amobile terminal through the triangulation method using a mobilecommunication system which has been constructed. The locationmeasurement technology using mobile communication includes anetwork-based scheme of finding the location of a terminal throughcooperation between a base station of a serving cell of the terminal anda neighboring base station, a terminal-based scheme in which a terminalhaving a GPS receiver, separately from a base station, transmitslocation information to a network, and a mixed scheme in which the twoschemes are combined. These technologies do not require a separateinfrastructure, and have wide service coverage, similar to the GPS,thereby being widely utilized as a macro-positioning technology.However, the technologies have a disadvantage in that the technologiescan be used only within a cell radius around a base station and inmetropolitan areas where radio waves can be received, and accuracy isdegraded indoors due to diffraction by propagation characteristics,multiple paths, and signal attenuation.

The location awareness technologies using the satellite communication ormobile communication are suitable for an outdoor environment because ofwide service coverage, but the location awareness technologies arerestricted in shadow areas or indoors. Therefore, recently, research isbeing actively conducted into positioning methods using various wirelesscommunication technologies, such as diffuse-infrared, ultrasonic wave,radio frequency (RF), ultra wideband (UWB), and radio frequencyidentification.

DISCLOSURE Technical Solution

Most of these technologies calculate locations by using a differencebetween transmission speeds of ultrasonic waves, or by measuring asignal transmission distance according to signal attenuation obtainedthrough measurements of the signal strength (i.e. RSSI) of an RF signal.In the case of using the RSSI, since the characteristics of the RFsignals vary depending on the environments, there are defects in that itis difficult to accurately measure a location, and that an error rate ishigh. In the case of using the ultrasonic waves, there are defects inthat the ultrasonic waves are sensitive to directions due to thecharacteristics of sound waves, and that equipment is heavy.

Therefore, the present invention has been made in view of theabove-mentioned problems, and it is an object of the present inventionto provide a location measurement method for easily and accuratelymeasuring a location of a moving radio frequency identification (RFID)reader in an RFID system, and the same RFID system, in such a mannerthat the RFID system includes a plurality of beacon devices, which arefixed at predetermined locations and emit beacons including referencelocation information about their own reference locations andsignal-intensity-to-distance information, and that the RFID readerreceives beacons from at least three beacon devices, identifies relativedistances from the respective beacon devices by usingsignal-intensity-to-distance information included in the beacons, andcalculates its own location through a triangulation method.

In order to achieve the above-mentioned object, there is provided aradio frequency identification (RFID) system for measuring a location ofan RFID reader by using a beacon, the system including: a plurality ofbeacon devices for emitting beacons; an RFID tag for transmittingpre-stored information by using radio frequency identification; and anRFID reader for calculating a current location by using a plurality ofbeacons when the RFID reader 120 receives the plurality of beacons fromthe plurality of beacon devices while moving, and receiving theinformation from the RFID tag by using the radio frequencyidentification.

According to another aspect of the present invention, there is provideda method for calculating a current location by a radio frequencyidentification (RFID) reader in an RFID system, which includes an RFIDtag, the RFID reader, and a plurality of beacon devices, the methodincluding the steps of: (a) receiving a plurality of beacons from theplurality of beacon devices; (b) calculating relative distances from theplurality of beacon devices by analyzing the plurality of beacons; and(c) identifying reference locations of the plurality of beacon devicesby analyzing the plurality of beacons, and calculating the location byusing the reference locations of the plurality of beacon devices and therelative distances from the plurality of beacon devices.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram schematically illustrating the configurationof a radio frequency identification (RFID) system for measuring thelocation of an RFID reader by using beacons according to an exemplaryembodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for measuring the locationof an RFID reader by using beacons according to an exemplary embodimentof the present invention;

FIG. 3 is a view illustrating a situation where a beacon device emits abeacon according to an exemplary embodiment of the present invention;

FIGS. 4A and 4B are views explaining an example of a procedure ofmeasuring the current location by an RFID reader according to anexemplary embodiment of the present invention; and

FIG. 5 is a view explaining an example of a procedure of measuring amoving speed and a moving direction by an RFID reader according to anexemplary embodiment of the present invention.

MODE FOR INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. First, it is tobe noted that the same elements are indicated with the same referencenumerals throughout the drawings. In the following description, adetailed description of known functions and configurations incorporatedherein will be omitted when it may make the subject matter of thepresent invention rather unclear.

FIG. 1 is a block diagram schematically illustrating the configurationof a radio frequency identification (RFID) system for measuring thelocation of an RFID reader by using beacons according to an exemplaryembodiment of the present invention.

According to an exemplary embodiment of the present invention, the RFIDsystem for measuring the location of an RFID reader by using beaconsincludes a first beacon device 110, a second beacon device 112, a thirdbeacon device 114, an RFID reader 120, and an RFID tag 130.

The first to third beacon devices 110, 112, and 114 according to anexemplary embodiment of the present invention are fixedly installed atpredetermined locations in the RFID system and emit their respectivebeacons so that the RFID reader 120 can measure its own currentlocation. In this case, the beacon may be emitted as various wirelesssignals, such as an RF signal, a Zigbee signal, a Bluetooth signal, etc.

Also, each of the first to third beacon devices 110, 112, and 114according to an exemplary embodiment of the present invention emits abeacon, including reference location information about a referencelocation where the beacon device is positioned, andsignal-intensity-to-distance information, in which the circumstances ofan area where the beacon device is positioned are reflected.

To this end, each of the first to third beacon devices 110, 112, and 114according to an exemplary embodiment of the present invention includes abeacon emission means for emitting a beacon, a memory for storingreference location information and signal-intensity-to-distanceinformation, and storing software which controls the pieces ofinformation to be included in a beacon and to be emitted and whichcontrols the entire operation of the corresponding beacon device, and amicroprocessor for executing the software stored in the memory. Thefirst to third beacon devices 110, 112, and 114 may also be referred toas beacon transmitters.

Here, the reference location information represents three-dimensionalcoordinates (x axis, y axis, z axis) of a location where each beacondevice is positioned. The signal-intensity-to-distance informationrepresents information about relative distances (i.e. straight distancesregardless of direction) from the reference location of each beacondevice to the RFID reader 120 according to signal intensities of beaconsreceived by the RFID reader 120 from the beacon device, where thepropagation environment of an area where the beacon device is positionedis reflected in the information. The reference location information andthe signal-intensity-to-distance information will be described later indetail with reference to FIG. 3.

Meanwhile, although FIG. 1 shows the case where the RFID system formeasuring the location of a RFID reader using beacons according to anexemplary embodiment of the present invention includes only three beacondevices 110, 112, and 114, four, five, or more beacon devices may bedistributed in the RFID system.

The RFID reader 120 according to an exemplary embodiment of the presentinvention communicates with the RFID tag 130, and acquires informationstored in the RFID tag 130 through the communication.

Also, receiving beacons from the first to third beacon devices 110, 112,and 114, the RFID reader 120 according to an exemplary embodiment of thepresent invention analyzes beacons received from each beacon device 110,112, and 114, identifies the reference location information of eachbeacon device 110, 112, and 114, and the signal-intensity-to-distanceinformation of each beacon device 110, 112, and 114, and calculates itsown current location by using the reference location information and thesignal-intensity-to-distance information.

In this case, the RFID reader 120 measures the signal intensity of eachbeacon received from each beacon device 110, 112, and 114, calculatesrelative distances from the beacon devices 110, 112, and 114 byassociating the measured signal intensity of each beacon with thesignal-intensity-to-distance information of each corresponding beacondevice 110, 112, and 114, and calculates the current location throughthe triangulation method using the relative distance from each beacondevice 110, 112, and 114 and the reference location information of eachbeacon device 110, 112, and 114. A procedure where the RFID reader 120calculates the current location through the triangulation method will bedescribed later in detail with reference to FIGS. 4A and 4B.

Also, the RFID reader 120 according to an exemplary embodiment of thepresent invention receives beacons from at least three beacon devicesamong a plurality of beacon devices in order to calculate the currentlocation. That is, as described above, the RFID system for measuring thelocation of an RFID reader using beacons according to an exemplaryembodiment of the present invention may include three or more beacondevices. The RFID reader 120 must receive beacons from at least threebeacon devices in order to calculate the current location. Therefore,when receiving beacons from four or more beacon devices, the RFID reader120 uses beacons received from three beacon devices, from whichrelatively higher signal intensities of beacons have been received, inorder to calculate the current location.

Also, the RFID reader 120 according to an exemplary embodiment of thepresent invention measures the locations thereof while moving, andcalculates a moving speed and a moving direction. That is, when the RFIDreader 120 has moved after measuring a current location (pre-movinglocation), the RFID reader 120 measures a current location (post-movinglocation) at a location after the movement, measures a movement timefrom the pre-moving location to the post-moving location, measures amoving distance from the pre-moving location to the post-movinglocation, and calculates a ratio of the moving distance to the movementtime as a velocity. In addition, the RFID reader 120 calculates a vectorfrom the pre-moving location to the post-moving location, therebycalculating a moving direction. A method of calculating a moving speedand a moving direction by the RFID reader 120 will be described later indetail with reference to FIG. 5.

FIG. 2 is a flowchart illustrating a method for measuring the locationof an RFID reader by using beacons according to an exemplary embodimentof the present invention.

Each of the first to third beacon devices 110, 112, and 114, which areseparately and fixedly installed in the RFID system, continuously emitsa beacon, including its own reference location information and thesignal-intensity-to-distance information according to the propagationenvironments thereof (step 210).

The RFID reader 120, which is moving within the RFID system, receivesthe beacons emitted from the first to third beacon devices 110, 112, and114 (step 220), and identifies relative distances from the beacondevices 110, 112, and 114 by analyzing the beacons received from thebeacon devices 110, 112, and 114 (step 230).

The RFID reader 120 calculates the current location through thetriangulation method using the relative distances from the beacondevices 110, 112, and 114 and the reference location information of eachbeacon device 110, 112, and 114 (step 240).

Meanwhile, when the RFID reader 120 has moved after calculating thecurrent location, the RFID reader 120 can measure a current locationeven at the post-moving location according to the procedure of steps 210to 240.

Therefore, when the RFID reader 120 has moved (step 250), the RFIDreader 120 measures a movement time from the pre-moving location to thepost-moving location (step 260), and measures the post-moving location(step 270). Then, the RFID reader 120 calculates a moving speed bydividing a distance from the pre-moving location (i.e. the currentlocation measured in step 240) to the post-moving location (i.e. thelocation measured in step 270) by the movement time measured in step260, and calculating a moving direction by calculating a vector from thepre-moving location to the post-moving location (step 280).

FIG. 3 is a view illustrating a situation where a beacon device emits abeacon according to an exemplary embodiment of the present invention.

Each beacon device 110, 112, and 114 emits a beacon so that the RFIDreader 120 can measure the location of the RFID reader 120, wherein thebeacon is attenuated according to distance, so that the power of anemitted beacon decreases as the emitted beacon becomes more distant fromeach corresponding beacon device 110, 112, and 114.

In this case, the signal attenuation is influenced mostly by thepropagation environment according to circumstances of each beacon device110, 112, and 114. That is, when there is a factor causing large signalattenuation, such as a case where buildings and/or structures aredistributed or a high power line passes around a specific beacon device,a signal attenuation rate is very high, so that an available emissiondistance is shortened. In contrast, when such an attenuation factor issmall, a corresponding beacon device can emit a beacon for a longerdistance.

Therefore, since each beacon device 110, 112, and 114 is fixedlyinstalled, it is possible to create a database by measuring signalintensities of a beacon according to distance based on a propagationenvironment when each beacon device has been installed and thecircumstances of the beacon has been determined.

That is, when a specific beacon device emits a beacon, as shown in FIG.3, a database of signal-intensity-to-distance information can be createdas Table 1 below.

TABLE 1 Power (dbm) Range (m) 0 1 −1 1.5 −3 6.3 −5 10.3 −7 14 −10 21 −1535 −25 44

Therefore, the specific beacon device emits a beacon, including its ownreference location information and the signal-intensity-to-distanceinformation as shown in Table 1.

In a state where the specific beacon device emits a beacon, as shown inFIG. 3, when the RFID reader 120 receives the beacon from the specificbeacon device and obtains −10 dBm as a result of measurement of thesignal intensity of the beacon, the RFID reader 120 can identify adistance of 21 meters corresponding to −10 dBm by checking thesignal-intensity-to-distance information included in the beacon, so thatthe RFID reader 120 can recognize that the RFID reader 120 is located ata distance of 21 meters from the specific beacon device. It goes withoutsaying that a distance of 21 meters is a relative distance because it isnot a two-dimensional distance, but a three-dimensional distance.

Here, when it is assumed that the specific beacon device corresponds tothe first beacon device 110, the second beacon device 112 and the thirdbeacon device 114 also can emit beacons, as shown in FIG. 3. However,since the second beacon device 112 and the third beacon device 114 maybe under different propagation environment from the first beacon device110, signal attenuation rates may be different, so that each piece ofsignal-intensity-to-distance information included in beacons by thesecond beacon device 112 and third beacon device 114 may be differentfrom that shown in Table 1.

That is, since the first to third beacon devices 110, 112, and 114 areunder different propagation environments, and thus attenuation rates ofbeacons emitted from the beacon devices 110 to 114 are different,distances to which beacons having the same signal intensity can reachmay be different. Therefore, each of the first to third beacon devices110, 112, and 114 makes a database of signal-intensity-to-distanceinformation through measurements in advance, creates a table shown inTable, and emits the signal-intensity-to-distance information through abeacon so that the RFID reader 120 can exactly measure the currentlocation.

FIGS. 4A and 4B are views explaining an example of a procedure ofmeasuring the current location by an RFID reader according to anexemplary embodiment of the present invention.

FIG. 4A is a view explaining an example of a procedure of identifying,by an RFID reader, relative distances from beacon devices according toan exemplary embodiment of the present invention.

In a state where the first to third beacon devices 110, 112, and 114 arefixedly installed, the RFID reader 120 is located within beacon emissionranges of the three beacon devices, as shown in FIG. 4A, and the RFIDreader 120 receives a first beacon, a second beacon, and a third beaconfrom the beacon devices 110, 112, and 114.

The RFID reader 120 measures the signal intensities of the first tothird beacons received from the beacon devices 110, 112, and 114,respectively. When it is assumed that the signal intensity of the firstbeacon is 0 dBm, the signal intensity of the second beacon is −25 dBm,and the signal intensity of the third beacon is −7 dBm, as shown in FIG.4A, the RFID reader 120 can identify distance “d1” corresponding to 0dBm by checking first signal-intensity-to-distance information includedin the first beacon, can identify distance “d2” corresponding to −25 dBmby checking second signal-intensity-to-distance information included inthe second beacon, and can identify distance “d3” corresponding to −75dBm by checking third signal-intensity-to-distance information includedin the third beacon.

FIG. 4B is a view explaining an example of a procedure where the RFIDreader 120 calculates the current location by using the relativedistances from the beacon devices and the reference location of eachbeacon device according to an exemplary embodiment of the presentinvention.

After identifying relative distances from the beacon devices 110, 112,and 114 by measuring the signal intensity of each beacon (i.e. each ofthe first to third beacons) received from each beacon device 110, 112,and 114, as described above with reference to FIG. 4A, the RFID reader120 identifies first reference location information, second referencelocation information, and third reference location information includedin the beacon, i.e. in the first beacon, the second beacon, and thethird beacon, respectively.

Here, the first reference location information, the second referencelocation information, and the third reference location informationcorrespond to three-dimensional coordinate information about the x-axisy-axis and z-axis coordinates of the beacon devices 110, 112, and 114,respectively.

Here, when it is assumed that the first reference location informationcorresponds to coordinates (x1, y1, z1), the second reference locationinformation corresponds to coordinates (x2, y2, z2), and the thirdreference location information corresponds to coordinates (x3, y3, z3),as shown in FIG. 4B, the RFID reader 120 can calculate the currentlocation through the triangulation method by means of the relativedistances from the beacon devices 110, 112, and 114, identified asdescribed above, and the three-dimensional coordinate information ofeach beacon device 110, 112, and 114.

That is, when the three-dimensional coordinates of the current locationof the RFID reader 120 correspond to (x, y, z), an equation for thecurrent location can be derived as equation 1 below by using thetriangulation method.(x1−x)²+(y1−y)²+(z1−z)²=(d1−err)(x2−x)²+(y2−y)²+(z2−z)²=(d2−err)(x3−x)²+(y3−y)²+(z3−z)²=(d3−err)   [Math FIG. 1]

In equation 1, “err” represents an error with respect to distance, andis a constant which can be determined according to a tolerable errorrate in the current location.

Also, “x1,” “y1,” “z1,” and “d1” correspond to the first referencelocation information and the relative distance from the first beacondevice 110, and are constants which can be identified from the firstbeacon. “x2,” “y2,” “z2,” and “d2” correspond to the second referencelocation information and the relative distance from the second beacondevice 112, and are constants which can be identified from the secondbeacon. “x3,” “y3,” “z3,” and “d3” correspond to the third referencelocation information and the relative distance from the third beacondevice 114, and are constants which can be identified from the thirdbeacon.

Therefore, since only “x,” “y,” and “z” correspond to variables to befound in three equations shown in equation 1, the three-dimensionalcoordinates (x, y, z) of the current location of the RFID reader 120 canbe obtained by solving the three simultaneous equations.

As described above, according to the present invention, at least threebeacon devices emitting beacons are fixedly installed in the RFIDsystem, and each beacon device 110, 112, and 114 emits a beacon,including reference location information of the beacon device andsignal-intensity-to-distance information where the propagationenvironment of the circumstances of the beacon device is reflected,which helps the RFID reader 120 to determine the current location. Then,the RFID reader 120 measures the signal intensities of a first beacon, asecond beacon, and a third beacon, which have been received from thebeacon devices 110, 112, and 114, respectively, identifies relativedistances corresponding to the signal intensities of the beacons,respectively, and calculates the current location by usingthree-dimensional coordinates of each beacon device 110, 112, and 114,so that the moving RFID reader 120 can measure its own location, andfurthermore, can exactly measure the location because the propagationenvironment of circumstances of each beacon device 110, 112, and 114 canbe reflected.

FIG. 5 is a view explaining an example of a procedure of measuring amoving speed and a moving direction by an RFID reader according to anexemplary embodiment of the present invention.

As described above with reference to FIGS. 4A and 4B, the RFID reader120 according to an exemplary embodiment of the present invention canmeasure its own current location by using at least three beacon devices.

Meanwhile, the RFID reader 120 can freely move in the RFID system, andcan continuously measure its own location, even while it is moving.Hereinafter, a procedure where the RFID reader 120 calculates ormeasures its moving speed and its moving direction while the RFID reader120 is moving in the RFID system will be described.

When it is assumed that the RFID reader 120 has moved from point A topoint B, point A corresponds to three-dimensional coordinates (x1, y1,z1), and point B corresponds to three-dimensional coordinates (x2, y2,z2), as shown in FIG. 5, a moving speed of the RFID reader 120 may bederived as equation 2.

$\begin{matrix}\frac{\sqrt{{\left( {{x\; 2} - {x\; 1}} \right)^{2}\left( {{y\; 2} - {y\; 1}} \right)^{2}} + \left( {{z\; 2} - {z\; 1}} \right)^{2}}}{{movement}\mspace{14mu}{time}} & \left\lbrack {{Math}\mspace{14mu}{Figure}\mspace{14mu} 2} \right\rbrack\end{matrix}$

That is, since a speed can be expressed as a ratio of a distance to atime, the RFID reader 120 can calculate a moving speed by dividing itsown moving distance by its own moving time. This is to calculate amoving speed by dividing a distance from a pre-moving location to apost-moving location by a moving time.

Also, a moving direction of the RFID reader 120 may be derived asequation 3.{right arrow over (d)}=(x2−x1,y2−y1,z2−z1)   [Math FIG. 3]

That is, a vector from x-axis, y-axis, and z-axis coordinates of apre-moving location to x-axis, y-axis, and z-axis coordinates of apost-moving location corresponds to a moving direction.

Therefore, the RFID reader 120 can calculate its moving speed and itsmoving direction by equations 2 and 3, can use the calculated movingspeed and moving direction to confirm if the RFID reader 120 isaccurately moving toward a destination, and can utilize the calculatedmoving speed and moving direction to calculate and estimate a directionand a speed in which the RFID reader 120 is to move to the destination.

Although an exemplary embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Therefore, the embodimentdisclosed in the present invention has been described not for limitingthe scope of the invention, but for describing the invention.Accordingly, the scope of the invention is not to be limited by theabove embodiment but by the claims and the equivalents thereof. It willbe understood by those skilled in the art that various changes in formand details may be made therein without departing from the spirit andscope of the invention as defined by the appended claims.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto measure the location of a moving RFID reader in an RFID system.

Also, since the location of the RFID reader is measured in considerationof propagation environments, it is possible to increase the accuracy ofthe location measurement.

In addition, since the RFID reader can measure its own location whilethe RFID reader is moving, it is possible to measure the moving speedand moving direction of the RFID reader.

The invention claimed is:
 1. A radio frequency identification (RFID)system for measuring a location of an RFID reader by using a beaconshort-range wireless communication system, the short-range wirelesscommunication system comprising: a plurality of beacon devicestransmitters, each of which is fixed at a reference location andcomprises an antenna, a processor and configured to create a database ofa memory having computer executable instructions stored thereon that,when executed by the processor, cause each of the beacon transmittersto: emit a beacon, wherein each of the beacon transmitters storesinformation about signal intensities to distances by measuring of thebeacon, the information about the signal intensities of the beaconaccording to distance distances having been obtained based on apropagation environment and emit the beacon which around each of thebeacon transmitters, wherein the beacon includes information about thereference location of each beacon device of the plurality of the beacontransmitters and the information about the signal intensities todistances from each beacon device; and an RFID reader configured toreceive the beacona means for receiving beacons from each of theplurality of beacon devices transmitters, measure a signal intensity ofeach received beacon, determine a distance from each beacon device byanalyzing the measured signal intensity on the basis of theextractinginformation about signal intensities to distances included in thereceived beacon and to calculate a current location thereof by usingbothfrom the received beacons, measuring signal intensities of thereceived beacons, determining distances from the respective beacontransmitters based on the measured signal intensities and theinformation about the signal intensities to distances, and calculatingthe location of the means based on reference location locations of theplurality of beacon transmitters and the determined distance distancesfrom each beacon device the plurality of beacon transmitters, whereinthe RFID reader calculates means is configured to calculate the currentlocation of the means through a triangulation method using based on thereference location locations of each beacon device the plurality ofbeacon transmitters and the determined distance distances from eachbeacon device the beacon transmitters.
 2. The system as claimed in claim1, wherein the RFID reader receives the plurality of beacons from atleast beacon transmitters include three beacon devices among theplurality of beacon devices or more beacon transmitters.
 3. The systemas claimed in claim 2, wherein, when receiving the plurality of beaconsfrom said at least more than three beacon devices transmitters, the RFIDreader means calculates the current location by of the means using threebeacons having relatively higher signal intensities among the pluralityof received beacons.
 4. The system as claimed in claim 1, wherein theRFID reader calculates means is configured to store the location of themeans at a first moment as a pre-moving first location and the locationand a post-moving thereof at a second moment as a second location, andcalculates the first moment being different from the second moment, andcalculate a speed and a moving direction of the means from thepre-moving first location to the post-moving second location, based on adistance from the first location to the second location and a timedifference between the first moment and the second moment.
 5. The systemas claimed in claim 4, wherein the RFID reader measures a movement timefrom the pre-moving location to the post-moving location, calculates adistance from the pre-moving location to the post-moving location, andthen calculates a ratio of the distance to the time as the speed meansis configured to calculate the moving direction by calculating a vectorfrom the first location to the second location.
 6. The system as claimedin claim 4, wherein the RFID reader calculates the direction bycalculating a vector from the pre-moving location to the post-movinglocation 1, wherein the short-range wireless communication system is aradio frequency identification (RFID) system, and the beacontransmitters are beacon devices.
 7. A method for calculating a currentlocation of a radio frequency identification (RFID) reader in an RFIDsystem by using a beacon of a beacon device in a plurality of beacondevices each of which is fixed at a reference location and configured tocreate a database of information about signal intensities to distancesby measuring signal intensities of the beacon according to distancebased on a propagation environment and emit the beacon which includesinformation about the reference location of each beacon device and theinformation about signal intensities to distances from each beacondevice the location of the means using the system of claim 1, the methodcomprising the steps of: (a) receiving a plurality of beacons from theplurality of beacon devices transmitters fixed at the referencelocations respectively; extracting the information about the signalintensities to distances from the received beacons; (b) measuring signalintensities of the plurality of beacons; and (c) received beacons;determining distances from the plurality of beacon devices by analyzingthe measured signal intensities on the basis of the information aboutsignal intensities to distances included in the plurality of receivedbeacons respective beacon transmitters based on the measured signalintensities and the information about the signal intensities todistances; and (d) calculating the location of each beacon device byusing the reference locations of the plurality of beacon devices and thedetermined distances in step (c) from the plurality of beacon devicesthe means through a triangulation method based on the referencelocations of the beacon transmitters and the determined distances fromthe beacon transmitters.
 8. The method as claimed in claim 7, where step(c) comprising the steps of: (c1) identifying information about thereference locations of the plurality of beacon devices, which isincluded in the plurality of beacons, by analyzing the plurality ofbeacons; and (c2) calculating the location through a triangulationmethod using the reference locations of the plurality of beacon devicesand the determined distances from the plurality of beacon devicesfurther comprising: storing the location of the means at a first momentas a first location; storing the location thereof at a second moment asa second location, the first moment being different from the secondmoment; and calculating a speed and a moving direction of the means fromthe first location to the second location, based on a distance from thefirst location to the second location and a time difference between thefirst moment and the second moment.
 9. The method as claimed in claim 7,further comprising, after step (c), the steps of: (d) moving the currentlocation to a next location; and (e) calculating a moving speed and amoving detection from the current location to the next location whereinthe plurality of beacon transmitters are beacon devices.
 10. A methodfor calculating a current the location of a radio frequencyidentification (RFID) reader the means of claim 1, the method comprisingthe steps of: receiving a beacon at the RFID reader beacons from each ofat least three beacon devices a plurality of beacon transmitters whichare disposed near the RFID reader, each beacon including first means,wherein the beacons include information about a reference locationlocations of each beacon device and second the beacon transmitters andinformation about signal intensities to distances from each beacondevice, respectively; retrieving at the RFID reader the firstinformation and the second information from each receivedbeaconextracting information about the signal intensities to distancesfrom the received beacons; measuring at the RFID reader a signalintensity of each received beacon signal intensities of the receivedbeacons; determining at the RFID reader a distance from each beacondevice by analyzing the measured signal intensity on the basis of theretrieved second information distances from the respective beacontransmitters based on the measured signal intensities and theinformation about the signal intensities to distances; and calculatingat the RFID reader the current location by using both the retrievedfirst information about the reference location and the determineddistance, wherein the each beacon device has a database of informationabout signal intensities to distances by measuring signal intensities ofthe beacon according to distance based on a propagation environment ofthe means through a triangulation method based on the referencelocations of the beacon transmitters and the determined distances fromthe beacon transmitters.
 11. The method as claimed in claim 10, whereinthe beacon transmitters are beacon devices.
 12. The method as claimed inclaim 10, wherein the beacon includes at least one of an RF signal, aZigbee signal and a Bluetooth signal.
 13. The method as claimed in claim1, wherein the beacon includes at least one of an RF signal, a Zigbeesignal and a Bluetooth signal.
 14. The system as claimed in claim 7,wherein the beacon includes at least one of an RF signal, a Zigbeesignal and a Bluetooth signal.